From: N295VV@aol.com
Message-ID: <0.abaaf288.259b1b80@aol.com>
Date: Wed, 29 Dec 1999 03:08:32 EST
Subject: Re: Tire Pressures and Shimmy-ES
To: lancair.list@olsusa.com
Mime-Version: 1.0

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From: David Jones

Hmmm.  The first thing Mike Dehate did when he came to check out my IV, was 
to put more pressure in the tires.  

In my IV, I use 50 lbs in the nose and 55 in the mains.  

 ( I use McCreary tires because the cutouts in the fuselage were originally 
made for that brand, and other profiles might bind on retraction--but that is 
no consequence to ES builders)

I suspect that your tire pressure is too low,  causing some harmonics that 
result in shimmy.  

I assume that you have adjusted your oleo pressure using a nitrogen bottle. 

If I had nose shimmy on a new plane, and all other remedies failed, I would 
switch tire brands, especially on an ES, where tire profiles make no 
difference in retraction--buying a different brand of tire is relatively 
inexpensive, and you can always reuse or sell the old ones if they are in 
good shape.  A different brand with higher pressure than you have now (which 
I think is too low a pressure) may solve your problem.

A final thought--lift your nose and recheck the tightness in the axle of the 
nose wheel.  If that has not loosened and seems ok,  you should check the 
tightness on the mains as well--jack the entire plane, remove the cotter pins 
and rotate the axle nut until it seems to bind the wheel when you spin it by 
hand.  Then back off the nut to the next castle flute, allowing the wheel to 
spin a little more freely.

Ohh, and one last suggestion.  All tires have a light side and a heavy 
side--marked by a red dot.  McCreary tires come with a sheet that tells where 
the red dot should be placed to keep the thing best in balance. (but at 2:00 
AM I'll be darned if i can remember where  the spot goes)

Good Luck,

David Jones, Pecatonica, Illinois


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